In such a clamping force adjust device (cf. prior German patent 4 018 284, corresponding to U.S. application Ser. No. 07/706,797, filed May 29, 1991 now U.S. Pat. No. 8,171,004, the housing is connected to a hollow spindle and formed as a hollow hand grip. The screw spindle engages in the movable jaw of a machine vise. The screw spindle is of hollow form and a tension rod is passed therethrough, with its first end connected to a force amplifier arranged below the fixed jaw. The adjusting sleeve is adjustable through a fine thread on the end of the tension sleeve facing the second end of the tension rod. The adjusting sleeve abuts the Belleville springs directly, these in turn abutting a thrust bearing. This thrust bearing furthermore lies on one side on the abutment flange of the tension sleeve and on the other side on the housing also. By rotating the adjusting sleeve relative to the tension sleeve the pre-tension of the Belleville springs changes and the desired clamping force can thus be preset. Especially with large clamp devices with a maximum clamping force of 40 kN or more, the spring force of the Belleville springs is however so great that a tool, for example, an open-ended spanner, is needed to adjust the adjusting sleeve and the adjustment can still only be effected with considerable effort.
The invention is therefore based on the problem of providing a clamping force adjusting device for a clamp device, especially a machine vise, of the kind initially referred to, in which the clamping force can be adjusted easily in the unstressed state by hand and without tools.
This is achieved according to the invention in that the abutment flange is provided on the end of the tension sleeve adjoining the second end of the tension rod and the thrust bearing is provided on the side of the abutment flange facing away form the second tension rod end, in that the Belleville springs are supported directly in the housing, in that an intermediate sleeve is provided between the Belleville springs and the thrust bearing, abutting the thrust bearing on one side and abutting the Belleville springs on the other side, and in that the adjusting sleeve can screw into a fine thread of the housing and has a radially inwardly directed first stop shoulder on its end facing the Belleville springs, this shoulder so cooperating with a radially outwardly directed second stop shoulder of the intermediate sleeve and/or a spacer ring bearing on the thrust bearing that the axial spacing of the first stop shoulder from the second stop shoulder or from the spacer ring is adjustable in the unstressed state by screwing the adjusting sleeve relative to the housing, whereby the stroke of the intermediate sleeve which this performs on tightening up to abutment of the first stop shoulder on the second stop shoulder or the spacer ring is adjustable.
Since the adjusting sleeve abuts neither the thrust bearing nor the Belleville springs in the unstressed state of the clamp device in the novel clamping force adjusting device, no axial forces act in the unstressed state. As a result the adjusting sleeve can be turned easily by hand without tools to alter the clamping force and thus easily adjust to the desired clamping force. This clamping force can be read easily off a scale applied to the adjusting sleeve. On adjusting to a minimum clamping force, the first stop shoulder has the greatest spacing from the second stop shoulder or the spacer ring. This spacing corresponds to at least the tightening stroke of the force amplifier. In the tightening stroke of the force amplifier the tension rod is so moved through the housing that ht tension sleeve approaches the Belleville springs. Through this the tension sleeve compresses the Belleville springs through the thrust bearing and the intermediate sleeve. The clamping force corresponds them to the spring force created by the compression of the Belleville springs. If the adjusting sleeve is on the other hand rotated relative to the housing for maximum clamping force, it moves the inwardly directed first stop shoulder with this adjustment of the clamping force up to the second stop shoulder or the spacer ring and comes into abutment therewith. Through this no mutual axial movement of the intermediate sleeve and the tension sleeve relative to the adjusting sleeve is possible in the tightening stroke of the force amplifier. The whole axial force transmitted to the tension rod in the tightening stroke of the force amplifier is transmitted directly from the tension sleeve through the thrust bearing and from this through the second stop shoulder or the spacer ring to the abutment shoulder of the adjusting sleeve and thence through the fine thread to the housing. The tightening stroke of the force amplifier leads to elastic deformation of the various components of the clamp device participating in the clamping, such as the tension rod, screw spindle, jaws and body of the clamp device. If the adjusting sleeve is set to a position between the maximum and minimum clamping forces, the spacing between its stop shoulder and the stop shoulder of the intermediate sleeve or the spacer ring is smaller than the tightening stroke of the force amplifier. In this case the belleville springs are firstly compressed to a certain extent in the tightening stroke, whereby a certain spring force is created. Then the stop shoulder of the adjusting sleeve comes int abutment with the stop shoulder of the intermediate sleeve or the spacer ring and the remaining, residual tightening stroke of the force amplifier now effects the elastic deformation of the components participating in the clamping. Since however the remainder of the tightening stroke is smaller than the maximum tightening stroke, a clamping force between the maximum and minimum clamping forces results.